Antares' Otrexup Approval Was Easy, Selling Drug Will be Hard

Doctors are unlikely to embrace Otrexup for rheumatoid arthritis patients without more efficacy data.

EWING, NJ (TheStreet) -- Antares Pharmaceuticals( (ATRS)) was granted U.S. approval for Otrexup on Monday. Easy. Actually selling the injectable formulation of methotrexate will be a lot more difficult.

Otrexup is a self-injection device that comes pre-filled with methotrexate for use by patients with rheumatoid arthritis. Methotrexate is a generic medicine, which, in pill form, is commonly prescribed to approximately 70% of the 1.5 million rheumatoid arthritis patients in the U.S. Injectable methotrexate is also available and delivers higher blood levels of the drug compared to pills. Despite its advantages, injectable methrotrexate is rarely prescribed, mainly because it requires a weekly visit to the doctor's office.

If you believe Antares' sales pitch -- the convenience of Otrexup (patients can self inject at home) will convince doctors to increase their use of injectable methotrexate for treating rheumatoid arthritis patients. If oral methotrexate is no longer effective, some patients might try Otrexup before moving on to biologic therapies like Abbvie's ( (ABBV)) Humira, Amgen's ( (AMGN)) Enbrel or Johnson & Johnson's ( (JNJ)) Remicade.

Antares plans a commercial launch of Otrexup in early 2014.

Don't expect Otrexup sales to roar out of the starting gate. This is a me-too drug, perhaps a bit more convenient. Rheumatologists and insurance companies aren't likely to embrace Otrexup.

The U.S. Food and Drug Administration approved Otrexup based on data showing the self-injector device was able to deliver higher blood levels of methrotrexate in patients compared to oral methotrexate. Fine, but the injectable methotrexate already used by rheumatologists also delivers superior levels of the drug into the blood -- and at a lower price.

Importantly, Antares has no data correlating higher blood levels of methotrexate to better outcomes for rheumatoid arthritis patients. Antares has not conducted a clinical trial to demonstrate use of Otrexup benefits patients any more than oral or conventionally injected methotrexate.

Without these comparative effectiveness data, Antares will have a tough time selling Otrexup.